A batch of newly discovered fossils come from prehistoric giant rhinos – the largest known land mammal in the history of the Earth.
Paleontologists discovered a complete skull from one rhino and three vertebrae from another, in the Linxia basin in the Gansu Province of northwestern China. The set of bones is 26.5 million years old.
Genetic analysis revealed that the fossils belonged to a species of giant rhino that scientists had never seen before. The team of researchers from China and the US dubbed the new animal “Paraceratherium linxiaense.”
“Usually fossils come in pieces, but this one is complete, with a very complete skull and a very complete jaw, which is rare,” Deng Tao, who led the team that discovered the fossils, told CNN. Deng is a professor at the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences.
Taller than a giraffe and roughly the size of six elephants, the rhino towered 23 feet above the ground, and its body was 26 feet long, Deng told CNN. It weighed roughly 24 tons. The skull was more than three feet long.
“It was very rare for a skull of that size to be preserved,” Deng said.
Deng and his colleagues shared their findings in a study published in the journal Communications Biology on Thursday.
A clue to the giant rhinos’ mysterious migrations
Scientists already knew about giant rhinos, or Paraceratherium, which have been found across Asia – mainly in Pakistan, Kazakhstan, Mongolia, and China.
But the new species, Paraceratherium linxiaense, shows that these prehistoric pachyderms made huge migrations across the continent.
In the early Oligocene era, 31 million years ago, giant rhinos moved out of the northern Tibetan plateau.
“Animal migration is linked to climate change. So 31 million years ago, when the Mongolian plateau dried up, they moved south,” Deng told CNN.
The new species, which is descended from those early migrants, indicates that giant rhinos made the trek back north during the late Oligocene. To get to Linxia, they would have had to cross the Tibetan plateau. According to Deng and his colleagues, this means the plateau must have been much lower than it is today.
“The weather got wet and they went back to the north,” Deng said. “Therefore, this discovery is of great significance to the study of the whole plateau-uplift process, climate, and environment.”
A ranger patrolling a watershed area east of Oakland, California discovered a trove of hundreds of fossils last summer from nearly a dozen ancient species. The site contains hundreds of petrified trees as well.
It’s one of the largest fossil finds in California history, and new fossils are still being unearthed there almost every day.
The discovery include fossils from prehistoric elephants with four tusks, mammoth-like mastodons, tortoises, and camels. The findingshave so far all been between 5 and 10 million years old.
The trove’s precise location remains a secret to protect the fossils and prevent looting.
The photos below show some of the findings so far.
Ranger Greg Francek was patrolling land in northern California last summer when he spotted a weird looking rock. “I was curious and had a closer look,” Francek told Insider.
The rock wasn’t a rock at all, but a petrified tree that was millions of years old.
“One end of the tree was partially exposed, and — to my surprise — I could see the tree rings,” Francek said.
The land Francek was patrolling is east of the San Francisco Bay — he has monitored watershed land for California’s East Bay Municipal Utility District (EBMUD) as a naturalist for more than a decade. Francek knew he’d come across something special, so he called paleontologist Russell Shapiro at California State University, Chico.
It wasn’t the first time Shapiro had been asked to look at potential fossils. “We get that call a lot,” he told Insider. But when Francek took Shapiro to see the ancient tree, they discovered a stunning trove of animal fossils.
“The very first day, I could look on the ground and go, ‘Well, that’s an elephant. That’s a rhinoceros. That’s a tortoise. That’s a camel,'” Shapiro said. “We found all this just by tripping over it.”
Shapiro knew it was an unprecedented discovery: Francek, it turns out, had stumbled across one of the largest fossil finds ever found in California.
“You kind of look around at the landscape and just think, ‘Oh, my god, there’s gonna be so much stuff here,'” Shapiro said.
In the 10 months since that first discovery, the duo has helped to unearth several hundred fossil specimens from nearly a dozen species. All are between 5 and 10 million years old.
Now, a team from EBMUD and CSU, Chico are steadily excavating the site. The fossils they’ve found offer a glimpse into an era of history known as the Miocene epoch, which occurred between 5 and 23.5 million years ago.
California looked quite different during the Miocene — there were no Sierra Nevada mountains, according to Shapiro, and dry grasslands were peppered with volcanoes. Still, the creatures that inhabited the land bore some resemblance to animals alive today.
Francek has discovered fossils of animals like rhinos, tortoises, and tapirs, which still exist, as well as extinct species like mastodons – shaggy, woolly mammoth-like beasts with tusks.
Shapiro recalled excavating a particular tapir jaw (pictured above) — he said he thinks tapirs are some of the cutest animals “because they look like a pig, but they have a nose like an elephant.”
Francek said it’s tough to pick a favorite fossil from the site, especially because he continues to find more whenever he visits.
“The giant camels are so cool. I like horses. And I like to think about the tortoises walking around the landscape like little armored tanks,” he said.
“I guess the creature that has my imagination working overtime is the gomphothere,” Francek added, “a four-tusked ancestor to the modern elephant.”
Gomphotheres were widespread in North America during the Miocene. They had tusks protruding from above and below their mouths.
Francek has found fossils from numerous gomphotheres, including an enormous, complete lower jaw and tusks.
That jaw, he said, “required 124 hours of excavation with hammer and chisel, and a tractor to lift it out of the ground.”
Shapiro said the team has unearthed countless herbivores but very few predator fossils. Ten months into the excavation, he said, “we’re just starting to find evidence of carnivores.”
In addition to fossils of weasel and fox relatives, they found evidence of bone-crushing dogs — prehistoric dog-like creatures that split off from the species that eventually became our pets.
These ancient dogs had strong jaws, Shapiro said: “They evolved the ability to chomp bone.”
He thinks these dogs were the dominant carnivores in the area millions of years ago, before they went extinct at the end of the Miocene.
The hundreds of fossilized trees found at the site so far can help scientists understand what happened to California’s climate at the end of the Miocene.
During those years, the Earth was starting to get colder, paving way for the first global ice age 2.4 million years ago.
“We can really tell that the temperatures were starting to drop quickly,” Shapiro said. “Right before this period, you find more tropical plants in California and elsewhere. And then right around this time, you’re seeing the spread of oaks and other plants like redwood trees that really prefer a cooler climate.”
Shapiro and Francek think the trove has more to offer. Francek said he’s been back to the site almost every day since last summer looking for new finds.
When he discovers something new, Francek takes photos, documents the location, contacts Shapiro, and starts trying to figure out what the critter might be. Recently, he uncovered a mastodon skull, complete with its tusks, fossilized in a rock.
“Every time he goes out, he finds something new, Shapiro said. “I’m getting used to him texting me photos almost every day.”
Once fully excavated, the fossils get taken to a lab in Chico. Shapiro said the team has finally secured a lab large enough to properly study all the findings. They’re working to count them and date the fossils more precisely.
“All of these bones come from pretty much one geologic layer,” Shapiro said.
That suggests the ancient creatures were fossilized around the same time.
The trove’s precise location remains a secret, however, in order to keep the area safe from vandals and looters.
Since excavations are ongoing, EBMUD does not allow the public to visit the site. Instead, it has set up an online tour of the findings for users to explore.
The secrecy is warranted: After Francek’s initial discovery, Shapiro recalled the ranger’s excitement at the prospect of showing him that first petrified tree. But when they arrived part of it was missing.
“It was like a punch to the gut to find that some of the petrified tree remains had been stolen and vandalized,” Francek said.
After that, the team quickly secured the remaining specimens and installed an around-the-clock patrol of the site.
“We intentionally waited nearly a year to announce the discovery so that we could establish solid security measures,” Francek added.
For all the awe Tyrannosaurus rex inspires, the “king of the dinosaurs” wasn’t very speedy.
Paleontologists already knew this predator was slow: It could only reach a maximum speed between 10 and 25 miles per hour. A 2017 study suggests that if a T. rex went any faster than 12 mph, the predator’s bones would have shattered – so it walked quickly to pursue its prey when needed.
But according to a study published Wednesday, T. rexes didn’t like walking fast if they could help it.
The researchers calculated that the dinosaur’s preferred walking speed was a 3-mph stroll.
That’s just under the average preferred walking speed for a human. So you could probably out-walk a T. rex, or at least keep up with one during its evening jaunt.
“Humans and T. rex would not, if the study is right, have had very different walking speeds,” John Hutchinson, an evolutionary biomechanics expert at the Royal Veterinary College in London who was not involved in the research, told Insider.
T. rexes preferred walking at the same speed that elephants do
An animal’s preferred walking speed enables it to move about using the least amount of energy possible, according to Pasha van Bijlert, the new study’s co-author.
While it may seem like the slower you walk, the less energy you use, that’s not necessarily the case. The best way to achieve maximum energetic efficiency is by finding a locomotion sweet spot known as resonance.
Imagine you’re swinging on a swing, trying to get it moving by swaying your legs back and forth. If you sway too quickly or too slowly, nothing happens. But undulating at just the right rhythm gets your body parts to resonate, and swing most efficiently.
A similar resonance happens when you’re walking at your preferred speed and your body finds a natural step rhythm.
“Many animals have a roughly similar preferred walking speeds: ostriches, elephants, giraffes, horses, gnus, and gazelles are the animals we’ve found data for, and they’re all not that fast when they don’t have to be,” van Bijlert told Insider. These animals prefer to walk between 2.2 and 3.1 mph, just like T. rex – and just like us.
That means the iconic scene from the 1993 film “Jurassic Park,” in which a T. rex chases a group of park visitors driving away, isn’t very accurate.
“I don’t think anybody believes a T. rex could outrun a Jeep, but it sure does make for a good movie,” van Bijlert said.
T. rex’s tail helped it walk efficiently
Researchers previously calculated T. rex’s walking speed by looking at fossilized footprints, then using the distance between those tracks to estimate the length of the dinosaur’s stride. Those earlier estimates suggested T. rex could walk as fast as 6.7 mph.
But instead of focusing on what T. rex’s legs were doing, van Bijlert’s group looked at the predator’s tail. A T. rex’s tail bobs up and down as it walks.
According to the study authors, every time T. rex’s tail sways up, ligaments inside the tail pull its legs backward, and store energy that then gets released when the tail swings back down. That energy propels the dinosaur forward.
The pace of that tail sway indicates T. rex’s natural step rhythm.
To figure how fast a T. rex tail would move, van Bijlert’s team created a 3D-model of an adult T. rex skeleton named Trix from the Naturalis Biodiversity Center in the Netherlands. The team reconstructed where all of Trix’s muscles and ligaments would start and end between her tail and legs, and used that model to help calculate her preferred walking speed: 2.9 mph.
Hutchinson said there’s some uncertainty around that result, however, because van Bijlert’s group didn’t take into account whether Trix’s tail would also be swinging side-to-side, and whether the muscles driving that motion might impact her top walking speed.
The new study doesn’t offer further insights into T. rex’s maximum speed, he added.
“There’s a big difference between a casual stroll in no rush versus a sprint,” Hutchinson said.
It would take an adult T. rex more than 13 hours of walking to patrol its territory
T. Rex’s preferred walking speed could tell us how long it took for the dinosaur to forage or scout an area, according to van Bijlert.
A new study from paleontologists the University of California, Berkeley suggested a single adult T. rex lived in an area roughly 40 square miles in size. So if a T. Rex went on a stroll to survey every part of its territory, the endeavor could take more than 13 hours.
T. rex was still a deadly predator, though, when moving at maximum speed.
A fully-grown T. rex was one of the largest carnivorous land animals that ever walked the Earth, standing about 12 to 13 feet tall at the hip and measuring up to 43 feet from tooth to tail. An adult T. rex could weigh between 5.5 and 9 tons – about the size of an adult African elephant.
T. rexes also had a keen sense of smell, acute vision, and excellent hearing, making it hard for prey to avoid detection. On top of that, their jaws had a bite force of 7,800 pounds, equivalent to the crushing weight of about three Mini Cooper cars. No other known animal could bite with such force.
“All evidence suggests it would have no issues capturing similar-sized prey,” Hutchinson said.
An adult Tyrannosaurus rex required a lot of space – and the prey therein – to survive.
According to new calculations from paleontologists the University of California, Berkeley, each adult T. rex lived in an area roughly 40 square miles in size.
The study, published Thursday in the journal Science, uses that math to offer an estimate of the total number of these predators that walked the Earth during the Cretaceous Period, between 66 and 68 million years ago: an impressive 2.5 billion.
“The total number did catch me off guard,” Charles Marshall, a paleontologist at Berkeley who co-authored the study, told Insider.
Marshall’s analysis suggests that the entire island of Manhattan or city of San Francisco would be the territory of a single T. rex.
He said he’d been wondering for years how unusual it really is to find a T. rex fossil: “When I hold a fossil in my hand, I always said to myself, ‘I know this is freakishly rare.’ But just how rare is it – one in a million or one in a trillion?”
Comparing the T. rex to the Komodo dragon
The T. rex was one of the largest carnivorous land animals that ever walked the Earth. (That accolade currently goes to the polar bear.) An adult Tyrannosaurus rex could weigh at least 5 tons. It stood about 12 to 13 feet tall at the hip and was about 40 to 43 feet long.
The larger predators are, the fewer of them can live in the same area, since there just isn’t enough food to sustain their massive size. This is known as Durham’s Law. So if researchers know how many calories a meat-eater needs to survive, they can calculate the number of predators per square mile.
While there’s no living predator that resembles the T. rex in size, Marshall compared the dinosaur’s energy needs to those of a Komodo dragon, the largest lizard on Earth.
Using that benchmark, he calculated that there could have been roughly 3,800 T. rex in an area the size of California at any given time – or just two in an area the size of Washington, DC.
There were about 20,000 adult T. rexes living at one time
Marshall’s team also needed to calculate three other variables to determine the total number of rexes that ever walked the planet: the total land area of suitable T. rex habitat, the dino’s average life span as an adult, and how long these predators existed on Earth.
By reviewing the locations of every T. rex fossil ever found, the study authors determined that the predator lived in about 888,000 square miles of North America – and nowhere else on Earth. Although the animal might have been able to survive in the area that’s now Siberia, Marshall said, he’d be surprised if any rex fossils were ever found outside the one continent.
Using that assumption about the T. rex’s geographic range, Marshall calculated that there could have been about 20,000 adult T. rexes alive at any given time in the species’ existence.
Figuring out how long the T. rex species was around was a bit easier – the oldest rex fossil ever found suggests the dinosaur walked the Earth for the last 2.5 million years of the Cretaceous Period, starting 68 million years ago. Then it went extinct after the Chicxulub space rock struck.
Finally, Marshall’s team calculated how long one generation of adult rexes lasted by looking at the average time span between when rexes became fully grown – at around age 15 – and when they died in their early 30s.
That means that in the 2.5 million years these animals were on Earth, there were about 127,000 generations of them. Multiply that number by 20,000, and you wind up with 2.5 billion T. rexes.
However, Marshall pointed out that this number doesn’t include baby or juvenile T. rexes. Those were excluded from the calculations because research suggests juvenile rexes were smaller and faster than their adult counterparts, so hunted different prey.
Marshall’s team’s estimate suggests that the remains of just one in every 80 million adult T. rexes have been found. Currently, there are about 32 well-preserved, adult T. rex skeletons in public museums worldwide, Marshall said.
That means we’ve only dug up 0.00000125% of all the adult T. rexes that ever lived.
About 66 million years ago, a space rock more than 6 miles wide collided with Earth, striking land that is now part of Mexico.
The impact sparked wildfires that stretched for hundreds of miles, triggered a mile-high tsunami, and released billions of tons of sulfur into the atmosphere. That gaseous haze blocked the sun, cooling the Earth and dooming the dinosaurs, along with 75% of all life on the planet.
But the origins of that dinosaur-killing rock, named Chicxulub, have remained a mystery.
Most theories suggest Chicxulub was a massive asteroid; hundreds of thousands of these rocks sit in a donut-shaped ring between Mars and Jupiter. But in a study published Monday, two Harvard astrophysicists suggested an alternate idea: that Chicxulub wasn’t an asteroid at all, but a piece of shrapnel from an icy comet that had been pushed too close to the sun by Jupiter’s gravity.
Asteroids and comets are both classified as space rocks by NASA, but they differ in key ways: Comets form from ice and dust outside our solar system and are generally small and fast-moving, whereas rocky asteroids are larger, slower, and form closer to the sun.
“We are suggesting that, in fact, if you break up an object as it comes close to the sun, it could give rise to the appropriate event rate and also the kind of impact that killed the dinosaurs,” Avi Loeb, an astrophysicist and cosmologist at Harvard University and co-author of the new study, said in a press release.
The solar system acts like a ‘pinball machine’ for comets
Most asteroids come from the asteroid belt between the solar system’s inner and outer planets. But NASA scientists who keep tabs on space objects that pass near Earth have yet to figure out where Chicxulub came from.
In the new study, published in the journal Scientific Reports, Loeb and his co-author, Amir Siraj, suggest Chicxulub didn’t come from the asteroid belt. Rather, they say it more likely originated outside our solar system, in an area called the Oort cloud.
Think of the Oort cloud as ring made of 1 trillion pieces of icy debris, which sits beyond the farthest reaches of the solar system, surrounding it. It’s located at least 2,000 times farther away from the sun than Earth is. Comets that originate in the Oort cloud are known as long-period comets because they take so long to complete one orbit around the sun.
But these comets can sometimes get pulled off-course by the gravity of massive planets like Jupiter. Such a tweak to a comet’s orbit could send it hurtling on a path much closer to the sun.
“The solar system acts as a kind of pinball machine,” Siraj said in the release.
Comets that get near the sun are called “sungrazers.” The new study calculated that about 20% of Oort cloud comets are sungrazers. As they approach our star, its gravity starts to pull them apart. Fragments of comet slough off and may careen toward nearby planets.
This, the study authors say, is “a satisfactory explanation for the origin of the impactor” that killed the dinosaurs.
The asteroid-versus-comet argument isn’t settled
Siraj and Loeb aren’t the only scientists who think a comet, not an asteroid, doomed the dinosaurs. A group of researchers from Dartmouth College similarly suggested in 2013 that a high-speed comet could have created the Chicxulub crater.
Chicxulub hit Earth at a speed of 12 miles per second (43,200 mph), which is about 30 times faster than the speed of a supersonic jet. The resulting 100-mile-wide crater extended 12 miles into the depths of the Gulf of Mexico. Some scientists have estimated the asteroid’s power was equivalent to 10 billion of the atomic bombs used in World War II.
But not all researchers are convinced a comet caused that destruction.
Natalia Artemieva, a senior scientist at the Planetary Science Institute in Arizona, told The New York Times that comet fragments from a sungrazer would have been too small to create the Chicxulub crater. And Bill Bottke, a planetary scientist at the Southwest Research Institute in Colorado, suggested that the study overestimates the frequency of sungrazers – and, consequently, the amount of fragments those comets produce.
Existing evidence favors the idea that Chicxulub was an asteroid, “but it’s not conclusive,” Bottke told the Times. “There’s still wiggle room if somebody really wants it to be a comet. I just think making that case is really hard.”
Siraj and Loeb, however, said their theory is supported by a type of material found deep inside the Chicxulub crater and other craters in South Africa and Kazakhstan. That substance, carbonaceous chondrite, may have come from comets. Whereas just 10% of asteroids from the asteroid belt are composed of carbonaceous chondrites, the material “could potentially be widespread in comets,” the study authors wrote.
The only samples ever collected from a comet in space were brought back in 2006. They revealed that object, called Wild 2, was composed of carbonaceous chondrite.
Finding the correct answer in the Chicxulub debate is useful because it could help researchers figure out the likelihood of a similar impact event in the future. Only two to three comets from the Oort Cloud have hit Earth during the last 500 million years, according to one study. By contrast, according to the Planetary Society, a Chicxulub-sized asteroid impacts Earth every 100 million years or so.
Siraj and Loeb modeled how many long-period comets get close enough to the sun to shed large fragments in the direction of Earth. Their numbers suggest 10 times more Chicxulub-sized objects hit Earth over its history than scientists previously thought.